From: Hannes Reinecke When specifying a different hardware handler via multipath features we should be able to override the built-in defaults. The problem here is the hardware table from scsi_dh is compiled in and cannot be changed from userland. The multipath.conf OTOH is purely user-defined and, what's more, the user might have a valid reason for modifying it. (EG EMC Clariion can well be run in PNR mode even though ALUA is active, or the user might want to try ALUA on any as-of-yet unknown devices) So _not_ allowing multipath to override the device handler setting will just add to the confusion and makes error tracking even more difficult. Signed-off-by: Hannes Reinecke Signed-off-by: Alasdair G Kergon --- drivers/md/dm-mpath.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) Index: linux-2.6.30/drivers/md/dm-mpath.c =================================================================== --- linux-2.6.30.orig/drivers/md/dm-mpath.c +++ linux-2.6.30/drivers/md/dm-mpath.c @@ -597,9 +597,20 @@ static struct pgpath *parse_path(struct } if (m->hw_handler_name) { - r = scsi_dh_attach(bdev_get_queue(p->path.dev->bdev), - m->hw_handler_name); + struct request_queue *q = bdev_get_queue(p->path.dev->bdev); + + r = scsi_dh_attach(q, m->hw_handler_name); + if (r == -EBUSY) { + /* + * Already attached to different hw_handler, + * try to reattach with correct one. + */ + scsi_dh_detach(q); + r = scsi_dh_attach(q, m->hw_handler_name); + } + if (r < 0) { + ti->error = "error attaching hardware handler"; dm_put_device(ti, p->path.dev); goto bad; }